refactor(shell): interpret zero timeout as unlimited execution

Replace unconditional WithTimeout usage with conditional context creation
based on timeout configuration. Zero values now bypass timeout enforcement,
using WithCancel for graceful cancellation while preserving existing timeout
behavior for positive values. Simplifies CronTool initialization by removing
unnecessary conditional timeout assignment.

pkg/tools/cron.go

@@ -28,11 +28,10 @@ type CronTool struct {
 }
 
 // NewCronTool creates a new CronTool
+// execTimeout: 0 means no timeout, >0 sets the timeout duration
 func NewCronTool(cronService *cron.CronService, executor JobExecutor, msgBus *bus.MessageBus, workspace string, restrict bool, execTimeout time.Duration) *CronTool {
 	execTool := NewExecTool(workspace, restrict)
-	if execTimeout > 0 {
-		execTool.SetTimeout(execTimeout)
-	}
+	execTool.SetTimeout(execTimeout) // 0 means no timeout
 	return &CronTool{
 		cronService: cronService,
 		executor:    executor,

pkg/tools/shell.go

@@ -89,7 +89,14 @@ func (t *ExecTool) Execute(ctx context.Context, args map[string]interface{}) *To
 		return ErrorResult(guardError)
 	}
 
-	cmdCtx, cancel := context.WithTimeout(ctx, t.timeout)
+	// timeout == 0 means no timeout
+	var cmdCtx context.Context
+	var cancel context.CancelFunc
+	if t.timeout > 0 {
+		cmdCtx, cancel = context.WithTimeout(ctx, t.timeout)
+	} else {
+		cmdCtx, cancel = context.WithCancel(ctx)
+	}
 	defer cancel()
 
 	var cmd *exec.Cmd